1. Field of the Invention
The present invention relates to a peer-to-peer (P2P) type communication system including a plurality of node devices mutually communicable through a network.
2. Discussion of Related Art
In this type of content delivery system, respective node devices have content catalog information, having attribute information (e.g. content name, genre, artist name) of content data in it, that are distributed to and stored in plural node devices, so that content data desired by users can be downloaded based on the attribute information, described in the content catalog information. Such the content catalog information is common information to be commonly used among plural node devices. Ordinarily the content catalog information is managed by a management server which manages all content data stored in the content delivery system and sent from the management server to the node devices in a response to a request of the node device.
For example, as this type of management server, Japanese Unexamined Patent Publication No. 2002-318720 discloses an index server that is located at the top of the hierarchy and manages all of the content information in the content delivery management system.
On the other hand, as a method of not using a management server, there are provided a pure P2P type delivery systems such as Gnutella, Freenet, and Winny. However, contents are searched by designating content names and keywords related to the content, location is identified and accessed. However, according to this method, users cannot use in such a way of viewing all content lists and access a desired content out of the lists, because there is no method of acquiring all lists of the content names.